Growing Ideas for Tomatoes
A sub-tropical tomato
Although sometimes called ‘tree tomato’, the tamarillo is a delicious sweet-sour fruit, which can be eaten raw or used in pies and preserves.
The tamarillo tomato (Cyphomandra betacea) is an attractive, sub-tropical shrub or small tree which produces delicious, plum-shaped fruit from early autumn on-wards. Unfortunately, the tamarillo has acquired the misleading name ‘tree tomato’, and is often listed as such in seed and nursery catalogues. In fact, tamarillos and tomatoes bear little resemblance to one another, apart from a superficial likeness of the fruit, although both are members of the Solanaceae family. The name ‘tree tomato’ is doubly misleading, because in cool temperate climates the plant rarely forms a tree, but instead makes a medium to large bush, occasionally reaching 4 m (12’) in height. The fruit, which hang attractively on long stalks from the branches, are 5-7.5 cm (2-3”) long, oval and slightly pointed at the end opposite the stalk. The thin, tough skins contain a pulpy flesh and a central core of numerous, edible seeds. In cross section they resemble tomatoes in their structure, but here the resemblance ends. The fully ripened fruit are either deep yellow-orange, bright red, or dark purple in colour, each with paler flesh inside. The taste of a ripe tamarillo is pungent and sweet-sour; unripe fruit is bitter and inedible. Many people consider the yellow-skinned tamarillo to be the mildest tasting, although the red-skinned variety is perhaps more visually attractive.
While the tomato is treated in the kitchen as a vegetable, the tamarillo is always served as a fruit. It can be eaten raw when fully ripe, after the skin has been peeled off. More frequently it is stewed and made into pies, preserves and chutneys, or else bottled or frozen. Tamarillos do not ripen all at once, and well-grown bushes may give you heavy supplies of fresh fruit well into winter, a time of year when fresh fruit is scarce.
A native of the mountainous regions of South America, it was long grown as a food crop by the Peruvian Indians. Since then, its cultivation has spread to East Africa, India and Sri Lanka, although it is only grown commercially on a large scale in New Zealand, where the warm climate and deep, well-drained sandy soils suit it best. Unlike other subtropical fruit, such as lemons, oranges and grapefruit, which you can always buy from the greengrocers, tamarillo fruit are virtually unavailable.
Being sub-tropical, tamarillos will survive in cool temperate climates only when given the protection of a greenhouse, conservatory, or warm, sunny room. Unlike aubergines, another tender member of the Solanaceae family, which are grown asand can give good crops outdoors in warm summers, tamarillos do not begin cropping until they are at least two years old. This means they have to live through the rigours of the raw, cold and wet English winters. Tamarillos are even more sensitive to frost than citrus trees, and so are quite definitely indoor subjects.
Their habit of growth is very attractive, though, with their very large, soft evergreen leaves and pale, greenish-pink flowers, and they are well worth growing as a decorative feature, either in a large pot, say 20-25 cm (8-10”) diameter, or in the greenhouse border.
In this country most tamarillos are grown from seed, which is very easily done. Sow them in spring in a seed; you will need to maintain a temperature of 24-27°C (75-80°F) for germination to take place. The young should be potted up into 7.5 cm (3”) diameter pots, and transplanted into larger and larger pots as the smaller containers are outgrown.
Alternatively, if you have a friend or neighbour with a strong growing tamarillo, you can take. These should be about 7.5 cm (3”) long. Inserted in a mixture of sandy in summer and kept at the same temperature as for seeds, they should root without much trouble.
Tamarillos thrive in a rich loam; mix two parts good loam (by volume) with one part leafmould and one part sharp sand, for drainage. Add a compound fertilizer at the rate of 90 g per sq m (3 oz per sq yd) at the same time, or 15 g (1/2 oz) per pot of the above size. Pot grown plants can be planted in their permanent beds any time of the year; remember to give them plenty of water if they are planted out in high summer. Tamarillos have very shallow rooting systems, so dryness at the roots can be disastrous. On the other hand, waterlogged soil is equally fatal, and during the winter the plants should receive only enough water to keep the leaves from wilting. Atmospheric moisture should also be avoided, because the soft young growth at the end of the stems is particularly vulnerable to botrytis in a damp atmosphere.
Even more important than moisture control is temperature control. Winter temperatures should not fall below 10°C (50°F), and the ideal temperature is more in the region of 16°C (60°F). If you have pot-grown plants, you can set the plant outdoors, in a sunny, sheltered place, from early summer through to early autumn, to ripen off the woody growth and hasten fruiting; bring the pot indoors again immediately the weather turns cold.
The tamarillo tomato has a lanky, straggling growth habit, so if you want to keep it relatively compact and attractive, pinch out the tips of leading shoots to force the plant to throw out new shoots towards the base of the stem. Do this in early spring, and at the same time thin out dead, diseased or overcrowded growth.
Tamarillo tomatoes fruit on the current year’s growth, so you should aim for a gradual replacement of old fruiting wood with strong new growth. Laterials which have finished fruiting should be cut back hard, otherwise fruit will eventually only form on the weaker, outer branches, leaving the centre of the shrub barren. These weak branches may snap under the weight of the fruit, and you will be left without any crop at all. Some people train them as standards, on a clean leg of about 90 cm (3’). Plants grown from seed tend to form this clean leg naturally, sometimes up to 1.8 m (6’) before branching. Although most young plants need some form of support, such as a bamboo cane, to begin with, after a few years the basal wood gets quite tough and hard, and the support can be dispensed with.
Only moderate feeding of border grown plants is called for; excessively rich growing conditions will lead to lush leaf growth at the expense of cropping. Pot-grown plants will need an annual mulch; scrape away the top 2.5 cm (1”) or so of compost and replace it with a rich mixture of potting compost and well-rotted manure. An occasional liquid feed high in potash will help in fruit production.
Although tamarillo flowers are normally self pollinating when grown out-of-doors, in greenhouse conditions it is best to hand-pollinate with a camel hair brush when the flowers are fully open.
If they are already in the greenhouse, whitcfly and red spider mite will feast on your tamarillo plants, which are particularly vulnerable to attacks by these pests. Control with insecticide sprays or fumigations.